We are primarily interested in the secretory adsorptive and microbial digestive processes which occur in the large intestine. Therefore we are examining the rate of digesta passage as well as the composition of digesta in the large intestine of wide range mammalian and a few other vertebrate species, under controlled conditions of diet, dietary regime and at selected times after feeding. In addition, we are conducting studies of secretory and absorptive mechanisms in a limited number of selected species by in vivo perfusion and in vitro mucosal transport procedures. BIBLIOGRAPHIC REFERENCE: Argenzio, R. A., J.E. Lowe and C.E. Stevens. Interrelationships of Na, HCO3 and volatile fatty acid transport across equine large intestinal mucosa. Gastroenterology 70:A-2/860, 1976 (abstract).